This disclosure refers to both particles and powders. These two terms are equivalent, except for the caveat that a singular “powder” refers to a collection of particles. The present invention may apply to a wide variety of powders and particles. Powders that fall within the scope of the present invention may include, but are not limited to, any of the following: (a) nano-structured powders (nano-powders), having an average grain size less than 250 nanometers and an aspect ratio between one and one million; (b) submicron powders, having an average grain size less than 1 micron and an aspect ratio between one and one million; (c) ultra-fine powders, having an average grain size less than 100 microns and an aspect ratio between one and one million; and (d) fine powders, having an average grain size less than 500 microns and an aspect ratio between one and one million.
Powders are used in a wide variety of applications. Currently, metallic powders (particles having a core that is either a pure metal or a metal alloy) are offered having an oxide shell. FIG. 1 is a cross-sectional side view of a metallic particle 100 having a metal, or metal alloy, core 102 covered by an oxide layer 104. As seen in FIG. 1, the oxide layer 104 can be quite thick, accounting for approximately 60% (sometimes more) of the entire size of the particle 100. This substantial oxide shell may be useful in certain applications. However, in other situations, it may be undesirable to have such a significant oxide presence.
SDC Materials, LLC has developed an in situ process that employs the use of flowing plasma and a vacuum system in order to produce particles having a reduced oxide layer. FIG. 2 is a cross-sectional side view of a metallic particle 200 resulting from such a process. The particle 200 has a metal, or metal alloy, core 202 covered by an oxide shell 204. As can be seen by comparing FIG. 2 to FIG. 1, the thickness of oxide layer 204 for particle 200 is significantly reduced from the thickness of oxide layer 104 for particle 100. Using this process, the thickness of the oxide layer can be reduced to less than 10% of the entire particle thickness. While providing a considerable improvement over the particle of FIG. 1, this process still does not achieve complete oxide removal from the particle. As a result, this nano-particle 200 may still prove to be undesirable for certain applications.
Currently, there is no way to create metallic particles having no oxygen. Even the best vacuum system has oxygen in it. As a result, the end product might not be sufficient for those who want oxide-free metallic powder.
What is needed in the art is a method for producing metallic powders that do not contain any oxygen.